This invention relates generally to sound reproduction in computer and audio systems and, more particularly, to stereo sound reproduction in a portable computer system.
High quality sound reproduction is commonly desired in present day computer systems. Many manufacturers offer speaker systems designed specifically for desktop computers. These systems can provide high volume and accurate reproduction across most of the human audible sound spectrum and typically employ conventional, electromagnetic speakers. Such speakers consist of a few electromagnetic speaker elements in an enclosure. The speaker elements are based on audio transducers, which utilize conical or other three-dimensional vibrating members. Conventional, electromagnetic speakers tend to be bulky or heavy.
Desktop computer speaker systems are typically too large, heavy, and fragile for portable use. Due to space and weight constraints, portable computersxe2x80x94which include variants such as laptops, notebooks, PDAs and so onxe2x80x94typically are equipped with small, conventional electromagnetic speakers built into the computer""s enclosure. These small, conventional speakers provide poor sound reproduction; their volume and reproduction of the audible spectrum are limited. Poor stereo separation is typical of portable computers due to the limited physical separation achievable for built-in speakers. In spite of these constraints, there exists an increasing demand for high quality, stereo sound reproduction in portable computer systems. Computer users increasingly choose portable computers for the convenience of a small, moveable system while traditional portable computer users, e.g. business travelers, continue to desire good sound reproduction for such applications as audio-visual presentations.
Because thinness is a desirable feature in portable computer configurations, use of speakers comprising a thin enclosure and good sound quality would be one approach to mitigate the portability problem of a computer system with good sound reproduction. Existing thin speakers, generally called xe2x80x9cplanar speakersxe2x80x9d, are usually based on two basic design types; electromagnetic and electrostatic. An electromagnetic planar speaker typically possesses a large, flat diaphragm and a set of relatively strong, permanent, strip magnets. The diaphragm is susceptible to tearing. An electrostatic planar speaker employs a very high voltage, which causes a susceptibility to arcing. Over time, arcing can destroy the electrostatic speaker""s diaphragm. Though planar speakers of a size suitable for portability can be produced by either of these existing approaches, such speakers would be expensive and lack the reliability of conventional electromagnetic speakers.
The additional problem of good stereo separation in portable computer systems can be solved by placing two speakers, i.e. the left and right sound reproduction channels, at some distance to either side of the portable computer. This complicates the problem of portability, however, because portable computer systems must be compact. A solution to the problem of stereo separation is desirable.
An object of the invention is to solve the problems of sound reproduction in portable computer systems: sound quality, i.e. accuracy and volume; stereo separation; durability; low cost; low power consumption; and portability.
In accordance with the present invention, a portable computer system includes: a base for holding electronic components that generate electrical signals; a lid that includes a monitor; and one or more planar speakers. A planar speaker is a thin audio output device that renders audio signals from electrical signals produced by the base. The thickness of each planar speaker is substantially less than the height or width of the planar speaker.
The flat, thin configuration of the planar speakers is achieved by a construction that includes a plurality of low cost, durable, electromagnetic speaker elements. These speaker elements are mounted on a panel in a coplanar arrangement and electrically connected with serial or parallel connections to obtain a desired impedance for the planar speaker. The panel and speaker elements are held within and protected by an enclosure. Sound equalization techniques can compensate for limitations in the sound reproduction spectrum of the individual speaker elements.
In one embodiment of the invention, two planar speakers are attached to the lid of the portable computer system. In one aspect, the planar speakers slide within the lid for storage. The planar speakers slide out of the lid to give greater physical separation than is possible with conventional built-in speakers. In another aspect, each planar speaker is attached to the lid via a hinge and folded against the lid when not in use. The planar speakers are folded outward so that they extend beyond the lid for use with greater physical separation than that of built-in speakers.
In another embodiment of the invention, the planar speakers are detachable from the lid. This permits an even greater spacing and variable positioning of the planar speakers for improved stereo sound reproduction. Detached planar speakers also permit transport or storage of the planar speakers separately from the remainder of the portable computer system.
Alternatively, the planar speakers can be used in portable music reproduction systems; in portable television sets; in aircraft to provide stereo audio to individual seats; or in a larger surface area form which includes hundreds or thousands of speaker elements for home audio reproduction systems.